Radiation therapy treatment plan development generally employs medical imaging, such as X-ray, computed tomography (CT), magnetic resonance imaging (MRI), or the like. Typically, a series of two-dimensional patient images, each representing a two-dimensional cross-sectional “slice” of the patient anatomy, are used to reconstruct a three-dimensional representation of a volume of interest (VOI), or structure of interest, from the patient anatomy.
The VOI typically includes one or more organs of interest, often including a planning target volume (PTV), such as a malignant growth or an organ including malignant tissue targeted for radiation therapy; a relatively healthy organ at risk (OAR) in the vicinity of a malignant growth at risk of radiation therapy exposure; or a larger portion of the patient anatomy that includes a combination of one or more PTVs along with one or more OARs. The objective of the radiation therapy treatment plan development typically aims to irradiate as much of the PTV as near the prescription dose as possible, while attempting to minimize irradiation of nearby OARs.
The resulting radiation therapy treatment plans are used during medical procedures to selectively expose precise areas of the body, such as malignant tumors, to specific doses of radiation in order to destroy the undesirable tissues. During the development of a patient-specific radiation therapy treatment plan, information generally is extracted from the three-dimensional model to determine parameters such as the shape, volume, location, and orientation of one or more PTVs along with one or more OARs.
Some existing radiation therapy planning tools have estimated irradiation doses of OARs based on the simple linear, or Euclidean, distance between the PTV and each OAR. However, additional factors typically have a significant impact on the effective radiation dose received by OARs in the general vicinity of the PTV. Existing methodologies can have drawbacks when used to develop radiation therapy plans, since existing methods and tools do not accurately account for these additional factors.